Chinese police investigating the apparent suicide attack in Beijing's Forbidden City suspect ethnic minority Uighur terrorists may be behind it.
They are searching for two ethnic Uighurs believed linked to the incident in which a car was driven into tourist crowds before exploding in flames, killing five people and injuring 38.
Radicals among the Muslim Turkic Uighurs have been fighting an insurgency against Chinese rule for years. This summer saw an unusually large number of violent incidents.
Police released no information about a possible motive for the attack at one of China's most politically sensitive and heavily guarded public spaces. But investigators are trying to trace the recent movements of the two suspects in Monday's attack, possibly uncovering any co-conspirators still at-large.
The car veered inside a barrier separating a crowded pavement from a busy avenue and then through pedestrians as it sped toward Tiananmen Gate, where it crashed into a stone structure near a large portrait of Mao Zedong, which hangs near the southern entrance to the former imperial palace.
The vehicle's three occupants were killed, along with two bystanders.
The gate stands opposite sprawling Tiananmen Square, which was the focus of the 1989 pro-democracy movement that was violently suppressed by the military, and any incident there is highly sensitive.
Police are searching for information about two suspects with Uighur names, asking hotels about them, and to report any suspicious guests or vehicles going back to October 1. One of the men, Yusupu Wumaierniyazi, was listed as living at the address of a town in the north-western Uighur homeland of Xinjiang in which 24 police and civilians and 13 militants were killed in an attack on June 26.
Uighurs are culturally, religiously and linguistically distinct from China's ethnic Han majority and many dislike heavy-handed Communist Party rule.
If intended as a political statement, Monday's attack could hardly have picked a more significant target. Just west of the square lies the Great Hall of the People, the seat of China's parliament, while many of China's top leaders live and work just a few hundred yards away in the tightly guarded Zhongnanhai compound.
The incident looked deliberate, the driver apparently jumped a curb and travelled about 400 yards to the spot where the car caught fire. Along the way, it avoided trees, street lights and at least one security checkpoint. The attackers also struck during the lunch hour when security would have likely been relatively slack.
In Xinjiang this year, dozens of people have been killed in clashes between security forces and Uighur militants, whom the government says have been inspired by global jihadist teachings. Authorities had earlier warned that extremists were planning attacks outside the region, although none have so far been reported.
However, the militants have inflicted relatively little damage because a smothering security blanket has made organisation difficult, denied them safe havens, and severely limited their access to firearms and explosives.